Mercury switch spinner head timing unit



Oct. 27, 1959 F. G. BOUCHER ET AL 2,910,645

MERCURY SWITCH SPINNERVHEAD TIMING 11km 2 Sheets-Sheet 1 Filed Aug. 14,1950 FIG.!

INVENTORS.

ATTORNEY Oct. 27, 1959 F. G. BOUCHER ETAL 2,910,645

MERCURY SWITCH SPINNER HEAD [TIMING UNIT Filed Aug. 14, 1950 2Sheets-Sheet 2 FIG.2

FIG. 4

INVENTURSV- FRANK G. BOUCHER BEN W. SEWELL FIG. 5

ATTORNEY United States Patent C) MERCURY SWITCH SPINNER HEAD TIMING UNITApplication August 14, 1950, Serial No. 179,112

8 Claims. (Cl. 32428) The present invention relates in general to acentrifugal tester for fuze safety switches, and relates moreparticularly to a spinner for testing delayed action mercury switches.

In certain electrically actuated fuzes, delayed action safety switchesof the mercury type are provided for keeping the firing circuitsshort-circuited until a predetermined time after the fuze has acquiredspin. These switches depend upon the shifting of a mass of mercury froman initial location, in which it forms a short circui-t across thefiring circuit, to another location to remove the said short circuit,such shifting being accomplished by centrifugally produced pressure thatcauses the mercury to flow through a resisting medium, such as a porouspartition. In spite of care in manufacture, it is not possible to makethese switches always identical in their delay characteristics, mainlybecause of certain unavoidable variations in the porous partition, andhence it is highly desirable to provide apparatus for determining thecharacteristics of the individual switches.

The object of the present invention, therefore, is to provide a spinnercapable of simulating the spin to which such switches are subjected inactual service, to determine the response of the switch.

A more specific object is to provide a variable-speed centrifugalspinner into which a mercury switch may be inserted for convenient andrapid testing, and in particular for determining the time required toopen the switch.

; Other objects and many of the attendant advantages of this inventionwill be appreciated readily as the same becomes understood by referenceto the following detailed description, when considered in connectionwith the accompanying drawings, wherein:

.Fig. lis a view partly in elevation and partly in axial section,through a mercury switch spinner embodying the invention, showing also adiagram of the electrical indicating circuit, the drive clutch being inits disengaged po:

sition, and the drive motor being partly broken away;

Fig. 2 is a corresponding partly elevational and partly axiallysectional view, showing the clutch in engaged position; a

. Fig. 3 is a cross-section through the spinner in the plane 33 of Fig.1, including also a fragmentary section in a lower plane, through abayonet joint;

Fig. 4 is an axial section, on a larger scale, through the spinner headand clutch, with a mercury switch in position to be tested; and

Fig. is a cross-section of the clutch, in plane 5-5 Fig. 4.

. Referring now to the drawings, and more particularly to Figs. 1 and 2,there is shown a spinner comprising a drive member in the form of a cup1 mounted on a vertical shaft S of a suitable motor M, capable ofrotating said cup at the desired speed of spin. For convenience, theapparatus may be mounted on a supp ort such as a table top T, throughwhich the cup 1 projects as shown, so that the motor M or other powersource is beneath the table, and thus out of the way. The cup 1 issecured to a reduced end of the shaft S as: by a headless set screw 2.The inside surface 3 of the cup preferably is cylindrical, so that thebottom of the cup is of the same diameter as the top. Near its upperend, the cup may have a sharply chamfered or frusto-conical portion 4with an annular groove 5 therein, to collect any lubricating oil thrownout by the centrifugal force.

A cylindrical casing 6 with an attaching flange 7, and open at bothends, surrounds the portion of the cup 1 that extends above the tabletop. Pins 8 are secured in the wall of the casing 6, near its upperedge. A cap 9 having a depending flange 10 cooperates with the casing 6as shown, and may be removably secured to said casing by means ofbayonet slots 11 formed in flange 10, to engage over the pins 8.

A shoulder 12 of the cap 9 provides a seat for a metal washer 13 whichfits within the flange 10 and is secured to the top of the cap 9 byscrews 14. This washer 13 has a central opening preferably slightlylarger than the bore of the cup 1, and, in conjunction with the top ofthe cap 9, provides support for several cylindrical pivoted clampingmembers 15, and an additional clamping member 16 which has a shaft 17extending through the top of cap 9. The clamping member 16 is mountedeccentrically upon its shaft 17, to which is secured a hub 18 having ahandle 19, the whole being so arranged that a substantially turn of thesaid handle in one direction or the other will. secure or release aswitch spinner head 20 with respect to said cover 9.

The said spinner head 20 is shown in detail in section, in Fig. 4. Itcomprises an upper head 21 made of insulating material, for example,Lucite, with two alined radial bores 22 and 23 formed therein. The bore22, which is usually of larger diameter than bore 23, serves to hold themercury switch 24 that is to be tested, while bore 23 contains acounterweight 25, secured in place by screws 26, to dynamically balancethe mass of the switch, to prevent excessive vibration when spinning. Ahelicoidal spring 27 is mechanically supported by a lug 28 on thecounterweight 25, and serves as an electric contact element, to makeconnection with the center contact 24a of the switch 24.

In orderto provide a circuit connection through these parts, aconducting plate 29 is mounted on the Lucite head 21, and a centralpressure-and-contact plate 30 is secured to the radially-inner end; ofsaid first plate 29, thus establishing metallic contact from said plate30 to the spring 27 and thence to the central inner contact 24a of theswitchundergoing the test. p V I Beneath the upper head 21 is mounted aclutch .jaw assembly that comprises two oppositely located clutch shoes,31 and 32. Theseshoes are connected to anintermediate metal cap 33 insuch way thatthey causesaid cap to rotate whenever the shoes arerotated, and as shown this is accomplished by securing the shoes toseparate hemicylindrical blocks 34 and 35, by means of screws 36. Theseblocks may be made of any suitable material, preferably of wood or aplastic, for greater lightness.

In order to allow the blocks to move toward and away from each other,they are, as seen in Fig. 4, mounted on studs 37 screwed into threadedbores 38 in the cap .33, said studs extending into bores 39 in therespective blocks, with a loose sliding fit, so that when the clutchassembly is rotated, the resulting centrifugal force will cause bothblocks to slide radially outward, and force the clutch shoes 31 and 32against the inner surface of the cup 1. H

An internally threaded lug 40 is provided in the center of the uppersurface of cap 9, and receives a correspondingly threaded tube 41,closed at its upper end bya-threaded cap 42,of.insulating materiaLhavinga cenralopeni g .43- Anin ula ing bu h ng .44 seats on ,a shoulder atthe bottom of lug 40, and an insulating tube 45 fits within the tube 41.A metal terminal plate 46 fits into the ,cap 42 and has ,a threaded stem47 with a nut .48 thereon, :to serve as ,xaiibinding-post.

Mounted for axial movement within the tube 45 is a metal rod 4-9, whichis guided by an enlargement '50 thereonditting in the-;bore of tube 45,and-by the opening 51 in bushingi. Saidflrod 49 is urged downward by ahelical spring 52, :whose upper end bears against plate 46, and whoselower end bears against the enlargement 50. As shown, the enlargement 50is most readily providedby a washer bearing against acotter-pin 53passing through rod 49. At its lowerend rod 49 carries ahardenedpressure element 54 (Fig. 4) such as a steel ball, for example, whichbears :on the contact plate 3.0.

An electrical circuit is shown diagrammatically as connecting theterminal plate 46 .to the frame of the motor M and thus to shaft S andcup 1. Thiscircuitcomprises a wire 55 clamped under the nut 48, andleading through a current indicating instrument 56 to one terminal of abattery 57, the other terminal of said battery being connected to theframe of the motor M through a wire 58.

The operation is as follows:

The cap 9 and the parts carried thereby are disconnected from the cup 1and housing 6 by a partial turn that releases the bayonet joints 8, 11.The switch 24 to be tested is pushed into the cavity 22 and held betweencenter-contact spring 27 and a retainer spring 59, which make electricalcontact respectively with the center contact 24a and the shell '24bofthe said switch. Next the head 20 is pushed as far as it will go,against the thrust of spring 52 and then clamped between members 15 and16 by means of handle 19.

The cap 9 is then secured to the housing 6 by means of the bayonetjoints, whereupon the parts will all be found positioned as shown inFig. 1. In this condition, the clutch members 31 and 32 are barely outof contact with the inner surface? of cup 1, and the spring 52 is undercompression. 7

Upon releasing the head 20 by turning the handle 19, said spring willimmediately push downward the head 20'and .the parts carried thereby,until the clutch shoes 31 and 32 rest on the bottom :60 of the cup 1, asshown in Fig. 2. Assuming that the shaft S is continuously turning thecup 1 at the desired speed, the clutch will at once start to rotate, dueto friction of the clutch shoes on the bottom of the cup, and thuscentrifugal force will come into play and force the clutch membersoutward firmly against the inner cylindrical surface of said cup,thereby rapidly accelerating the spin until the clutch is turning at thefull speed of the cup. j I

At a certain speed ofrotation the switch 24, due to centrifugal force,will push the end of the retaining spring 59 outward and into electricalcontact with the inner surface of cup 1, and thus will establish acircuit through the battery 57 and the indicating instrument 56. As thecontacts 24a and 24b of switch 24 at that time are still shorted by themercury 24c therein, the instrument 56 willshow a reading, indicatingthat current is flowing through said circuit. The instant at which thisattaining of proper spin speed occurs may be noted by a stop watch or byautomatic electric timing means, as preferred.

As the mercury 24c flows radially outward through the porous metalpartition 24d, due to the spin,;the switch 24 should become unshortedwithin a preset interval, and such unshorting will become manifest bythe return of the indicator reading to Zero. By timing thisevent, thedelay performance of the switch may thus be clocked and checked.Attention is called to the fact that a test of a mercury switch, as justdisclosed, is not injurious to the switch, which is restored to itsinitial condition after testing by reversing the switch 4 and thusapplying centrifugal force in the proper direction to .force the mercuryback to its original location. Thus all the switches that are to beactually used may be individually pretested, to make sure that each willoperate as intended.

Obviously many modifications and variations of the present invention arepossible :in the light of the above teachings. It is therefore to beunderstood that within the scope ofthe appended claims, the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

'1. A spinner for centrifugally testing delayed-action switches,comprising a driving clutch member, means for rotating said member, adriven head, a holder for the switch to be tested, carried by said'head,a driven clutch member secured .to said head, means for causing saiddriven clutch member to engage the driving clutch member to be rotatedthereby, and means providing an electric circuit through said switchwhile being rotated by said head, said circuit including also acontinuity indicator and a source of electric energy.

2. A spinner as defined in claim 1, wherein the .driving clutch memberis cup-shaped and whereinthe driven clutch member is at least partlywithin the said-driving clutch member, and has radially shiftable clutchshoes that become centrifugally engaged with the inner surface of saidcup-shaped driving clutch member.

3. A spinner for centrifugally testing delayed action switches,comprising a two-part clutch, the outer part of said clutch being a cup,a sourceof mechanical power rotating said cup, the inner part of theclutchbeing :located within the cup and having a head designed toreceive and hold the switch to be tested, a housing surrounding the cup,a cap detachably secured to the housing and resilient means carried bysaid cap and urging the two parts of the clutch into engagement whensaid cap is in place on the housing.

4. A spinner as defined in claim 3, wherein the cap has releasableclamping means for holding the inner-part of the clutch while said capis disengaged from the housing.

5. A spinner for centrifugally testing delayed action switches,comprising a clutch having a driving member, means maintaining saidmember in continual uniform rotation at the desired spin rate, saidclutch having a driven member, means maintaining said driven menrberinitially out of engagement with said driving member, but operable tocause such engagement at will, means mechanically connected to saiddriven member for holding the switch to be tested with its longitudinalaxis substantially normal to the axis of rotation of the clutch, meansestablishing an electrical connection to one terminal ofithe switch,centrifugal means establishing an electrical .connection to the otherterminal of the switch when the driven member attains a predeterminedspeed, and electrical means coacting with said connections and includingan indicator to show whether the switch is open or closed.

6. A spinner for centrifugally testing mercury delayed action switches,comprising, a support for a switch to be tested, means for rotating saidsupport about an axissubstantially normal to the longitudinal axis ofthe switch,

an open electrical circuit including the switch, a source of electricityand an indicator for disclosing the behavior of said switch, andcentrifugally actuated means for closing said electrical circuit onlyupon the attaining by the support of a predetermined rate of spin,thereby causing a flow of electricity from said source through theswitch and wherein such flow continues until the switch opens-at thetermination of its delay period.

7. A spinner arrangement as set forth in claim 6, wherein the means forrotating the support includes a driving member connected to a means forimparting rotational movement, a driven member -to which saidsupport issecured, and means maintaining said driven member out of engagement withsaid driving member but operable to cause such engagement, at will.

8. A spinner arrangement as set forth in claim 6, wherein saidelectrical circuit includes means establishing continuous electricalconnection at one terminal of said switch, and means restraining theestablishment of electrical connection at the other terminal of saidswitch until the predetermined rate of spin has been attained.

References Cited in the file of this patent UNITED STATES PATENTS

